Bexarotene (Targretin) belongs to a subclass of retinoids that selectively bind to and activates retinoid X receptors (RXRs), which have biological properties distinct from those of RARs. In vitro, bexarotene exerts antiproliferative effects on some tumor lines of hematopoietic and squamous cell origin.
Bexarotene is available in oral and topical formulations. Peak plasma levels are achieved within 2 hours of oral administration, although higher levels are obtained when the drug is ingested with a fatty meal. It is thought to be metabolized primarily by the hepatobiliary system, with a terminal half-life of approximately 7 hours.
Topical and oral bexarotene are approved for early-stage (patch and plaque) cutaneous T-cell lymphoma that is refractory to at least one other therapy. Oral bexarotene is also approved for refractory cases of advanced disease; however, the best response has been noted in early disease.
Local irritation, such as burning, pruritus, and irritant contact dermatitis, is common following topical application. Major side effects seen after systemic administration include dyslipidemia, leukopenia, liver function test abnormalities, and possibly development of cataracts. Unlike other systemic retinoids, oral bexarotene causes thyroid abnormalities in approximately half of patients, which may necessitate treatment for hypothyroidism. Bexarotene is teratogenic and should not be prescribed in topical or oral form to women of childbearing potential unless a negative serum pregnancy test has been obtained and the patient agrees in writing to use two effective forms of contraception from 1 month before to 1 month after treatment.
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